Concentrated airborne particles

Receptor Models. Receptor models, by their formulation, are effective in determining the contributions of various sources to particulate matter concentrations. In classic studies, sources contributing to airborne particle loadings have been identified in Washington, D.C. (78), St. Louis (9,24), Los Angeles (7,12), Portiand, Oregon (78), and Boston (79—81), as well as other areas including the desert (82). 

Other measurements important to visual air quality are pollutant related, i.e., the size distribution, mass concentration, and number concentration of airborne particles and their chemical composition. From the size distribution, the Mie theory of light scattering can be used to calculate the scattering coefficient (20). Table 14-2 summarizes the different types of visual monitoring methods (21). 

Evaporation at 20°C is negligible a harmful concentration of airborne particles can, however, be reached quickly when dispersed. 

The accident at the Chernobyl, Ukraine, nuclear reactor on April 26, 1986, contaminated much of the northern hemisphere, especially Europe, by releasing large amounts of radiocesium-137 and other radionuclides into the environment. In the immediate vicinity of Chernobyl at least 30 people died, more than 115,000 others were evacuated, and the consumption of locally produced milk and other foods was banned because of radiocontamination. The most sensitive local ecosystems were the soil fauna and pine forest communities. Elsewhere, fallout from Chernobyl measurably contaminated freshwater, marine, and terrestrial ecosystems, including flesh and milk of domestic livestock. Reindeer (Rangifer tarandus) calves in Norway showed an increasing frequency of chromosomal aberrations that seemed to correlate with cesium-137 tissue concentrations tissue concentrations, in turn, were related to cesium-137 in lichens, an efficient absorber of airborne particles containing radiocesium and the main food source of reindeer during winter. A pattern similar to that of reindeer was documented in moose (Alces) in Scandinavia. 

The basic assumption of these receptor models is that the ambient airborne particle concentrations measured at a receptor can be apportioned between several sources. In other words, each chemical element concentration at the receptor is considered as a linear combination of the mass fraction of the source contributions. 

Conventional studies generally involve the collection of an assemblage of airborne particles followed by determinations of the average or bulk concentrations of pollutant species present (12). However, the results often lack the analytical specificity required to identify particle sources, to determine particle speciation and reactivity, or to assess particle toxicity. 

There has been great interest in airborne particulate matter recently due to the results of a number of epidemiological studies showing a correlation between increased mortality and levels of airborne particles. Figure 2.14 shows one such correlation reported by Dockery et al. (1993). A clear relationship between mortality rates and the concentration of fine particles PM25, as well as with particle sulfate, is seen. Since sulfate is found primarily in fine particles, these observations are not independent. Schwartz et al. (1996) report a 1.5% increase in total daily mortality with an increase of 10 pg m-3 in PM25. Deaths due to chronic obstructive pulmonary disease increased by 3.3% and those to ischemic heart disease by 2.1%. 

Calculate the mole fractions of SO j, HSO, and SO3- in solution at a pH of 8.0, equal to that of seawater and therefore expected for airborne particles formed from seawater in clean regions as well as the total concentration of S(IV) in solution for 20 ppb S02 in the gas phase. Comment on the implications for the potential role of sea salt particles in the oxidation of S02 in the marine boundary layer. 

De Raat, W. K., and F. A. de Meijere, Polycyclic Aromatic Hydrocarbon (PAH) Concentrations in Ambient Airborne Particles... 

Humidifiers can be a significant source of airborne particles if tap water is used because as the water evaporates from the aerosol, the solids that were in water are left as particles. For example, Highsmith et al. (1988, 1992) showed that the airborne particle concentration increased linearly with the total dissolved... 

Naik, D. V., C. J. Weschler, and H. C. Shields, Indoor and Outdoor Concentrations of Organic Compounds Associated with Airborne Particles Results Using a Novel Solvent System, in Indoor Air Pollution—Radon, Bioaerosols, VOC s (J. G. Kay, G. E. Keller, and J. F. Miller, Eds.), Chap. 6, pp. 59-70, Lewis Publishers, Chelsea, MI, 1991. 

Monthly average 222Rn concentrations in air during 1959-1966, measured daily at 8 30 a.m. by counting a-particles emitted by the short lived 214Po daughter in 24-hour samples of airborne particles, showed an annual maximum in August-October and minimum in February-April. 

As reported by Olmez and Gordon (University of Maryland), the concentration pattern of rare earth elements on fine airborne particles (less than 2.5 micrometers in diameter) is distorted from the crustal abundance pattern in areas influenced by emissions from oil-fired plants and refineries. The ratio of lanthanum (La) to samarium (Sm) is often greater than 20 (crustal ratio is less than 6). The unusual pattern apparently results from tlie distribution of rare earths in zeolite catalysts used in refining oil. Oil industry emissions have been found to perturb the rare earth pattern even in very remote locations, such as the Mauna Loa Observatory in Hawaii. 

Morawska L, Jayaratne ER, Mengersen K, Jamriska M, Thomas S (2002) Differences in airborne particle and gaseous concentrations in urban areas between weekdays and weekends. Atmos Environ 36 4375 -383... 

Morawska L, Congrong H (2003) Particle concentration levels and size distribution characteristics in residential and non-industrial workplace environment. In Morawska L, Salthammer T (eds) Indoor environment airborne particles and settled dust. Wiley-VCH, Weinheim... 

Lingard JJN, Agus EL, Young DT, Andrews GE, Tomlin AS (2006) Observations of urban airborne particle number concentrations during rush-hour conditions analysis of the number based size distributions and modal parameters. J Environ Monit 8 1203-1218... 

Clean rooms are maintained under a state of operational control on the basis of dynamic (operational) data. Class limits are given for each class name. The limits designate specific concentrations (particles per unit volume) of airborne particles with sizes equal to and larger than the particle sizes shown in Table 2 [7,10-12,14],... 

Airborne particulate cleanliness shall be designated by a classification number N. The maximum permitted concentration of particles C for each considered particle size D is determined from the formula... 

Cn represents the maximum permitted concentration (in particles/m3 of air) of airborne particles that are equal to or larger than the considered particle size. Cn is rounded to the nearest whole number, using no more than three significant figures. 

Geochemical modeling is often used to identify the compounds that primarily control the chemistry of arsenic in aqueous solutions. Modeling studies indicate that the arsenic concentrations of Kelly Lake, Ontario, Canada, are controlled by the precipitation and dissolution of Fe(II) arsenates rather than calcium or Fe(III) arsenates (Sadiq et al., 2002). The arsenic in the lake originated from runoff from the nearby Sudbury mining district and airborne particles from local ore smelters (Sadiq et al., 2002). 

---